In underground mining in general, and in coal mining specifically, there is constant and well deserved attention paid to supporting the mine roof. There are a variety of ways in which roof support may be effected in "conventional" mines as well as in those mines which employ mining methods described as short wall and/or long wall mining. In "conventional" mines support is usually provided to a previously unsupported (and usually just mined) area of mine roof through conventional roof bolts and the like. These bolts are inserted into substantially vertically drilled holes into the mine roof by a bolter apparatus and generally have shapes, designs and lengths which depend, at least to a large extent upon the geographical makeup of the mine, the coal being mined, and the mine roof. The roof bolts with conventional, expandable, wedge-type members and bearing plates, as well as the "less conventional" and "newly" introduced resin bolts, tie the overhead strata together, thereby reducing and hopefully eliminating the possibility of roof falls. In the areas of conventional mining, where large blocks of coal are dislodged from the coal face, it is necessary to place these roof bolts along predetermined rows and files throughout the length and width of substantially all of the mined area. Moreover, there are federal, state and county regulations which stipulate exactly how much length of unsupported mine roof may be present between the last roof bolt and the coal face. These regulations are strictly followed by mine personnel because of the relationship between roof falls and unsupported mine roof areas between the last row of bolts and the face being mined. The gamble of men and equipment is far too great to extract coal and support the mine roof in any other way within "coventional" mining environments.
Under current mining regulations it is necessary, subsequent to the extraction of coal from the face, to move a portable self-propelled bolter vehicle into the haulageway and set both rows and files of roof bolts into the mine roof to reduce the length of unsupported roof. Generally, the maximum length of allowable unsupported roof is approximately 20 feet. When such a length has been reached, the coal miner is extracted and the bolting operation commences for that given area. The roof bolts which are set into the predrilled holes in the mine roof have center to center permissible distances of 4 feet with a maximum 4 foot distance between the rib and the next inward bolt. Due to the configuration of current designs, roof bolting machines currently available must drill and set successive series (usually three or four) of roof bolts (having a width of between two and four roof bolts) across the longitudinal axis of the haulageway, continuing down the haulageway until four rows have been set and the roof is again supported. Each of these successive lateral drilling series necessitates the retraction of temporary roof supports, the movement of the drilling vehicle four feet further into the passage and the positioning of the drilling machine so that the next series of holes drilled will be 4 feet from the last. Next, the temporary roof supports associated with the drilling apparatus must again be actuated for providing the necessary support for the mine roof during the drilling operation about to commence. It should become apparent that there is a bottleneck in the mining operation and that bottleneck is the roof drilling and bolting operation. It is necessary then, in order to increase mining efficiency, to decrease the time spent in the slowest operation which is holding up the rest of the mining operation. The fastest and most efficient mining machinery serves little good while a slow and cumbersome apparatus slows down the subsequent bolting operation.
The situation noted above is further complicated by the necessity for protecting the mine personnel operating the bolting apparatus during the drilling operation. In order to provide the operator with some protection from roof falls, it has been the practice to manually place temporary jack supports around the area to be drilled. Alternatively, large cantilevered hydraulically actuated arms may be used to provide some degree of protection to bolter personnel from the possibility of roof falls. The currently employed method and apparatus for accomplishing a bolting operation is slow and tedious on one hand and cumbersome on the other. Bolting still remains the "log" jamming the possible increase in coal extraction, the weakest link in the coal mining operation.